Several reports have demonstrated T regulatory cells may play an important role in the pathophysiology of immune thrombocytopenia (ITP). As the immunomodulator, bone-marrow-derived mesenchymal stem cells (MSCs) (BM-MSCs) regulate T regulatory cells and show therapeutic effects on autoimmune diseases. However, it is not clear how BM-MSCs affect ITP. In this study, we explored the specific effects of BM-MSCs on ITP in mice. Using a murine model of ITP, mice were randomly divided into three groups: normal control group, ITP control group and ITP and BM-MSCs group. Platelet (PLT) levels were monitored by an automatic blood cell counter, and T regulatory cells were analyzed by flow cytometry. Compared with the untreated ITP mice, the PLT level of the ITP mice was significantly increased after BM-MSCs treatment. In the BM-MSCs group, T regulatory cells were significantly decreased. These findings demonstrate that bone-marrow-derived MSCs are effective in improving PLT levels and reducing the T regulatory cells mediating proinflammatory response in ITP mice.